When I want a hard on I just add some playing cards to Linda's spokes like I did when I had my Schwinn Typhoon.

...and if you want extra loud, double up the playing cards. My bikes had 4 cylinder playing card engines....WOW...and my butt dyno said the 4 card was better than the 2 card setup. I did like the occasional single cylinder playing card setup however...mileage was better.